An oil well of the type having a pumpjack unit will usually have a string of sucker rod extending thousands of feet down the borehole to a downhole pump. From time to time it is necessary to pull the downhole pump and rod string for one reason or another and at this time it is prudent to clean, inspect, and replace any defective part of the string.
The rod string is made up from a plurality of rod joints, each coupled together by a cylindrical threaded coupling member, so that the string can be broken down into a stack of joints. This enables the sucker rod string to be pulled from and run back into the borehole, and facilitates handling and transporting the rod string. Inspection of the rod string therefore necessitates the removal of the coupling member from the opposed ends of the rod joints so that the rod joints, threads, and coupling member can all be thoroughly inspected.
Removing sucker rod couplings from a joint of sucker rods is a laborious task. One must not use high friction jaws, such as found on pipe wrenches, for engaging the coupling because the outer surface of the coupling must remain perfectly smooth and unmarred, otherwise a stress riser will be created and a crack will subsequently develop and the coupling will break. For this reason the rod joints have a wrench flat at opposed ends thereof adjacent to the coupling member so that two wrench flats adjacent to a coupling can be engaged by two open end wrenches in order to break the rod string down into joints. Hence, the coupling members are always left on the rod joint until it is necessary to remove them.
In the past, after the rod string has been broken down into joints, a large hand operated friction wrench with smooth jaws has been used for loosening the coupling from the sucker rod. The wrench flat of the rod is engaged with an open end wrench while the coupling is rotated with the friction wrench. It is often necessary to place sand between the jaws of the wrench and the coupling in order to increase the friction without harming the coupling surface. Because of the great torque previously used to tighten the coupling, it is usually necessary to add an extension pipe to the wrench handle in order to obtain enough leverage to loosen the threaded connection. This is a time consuming and often dangerous endeavor. The friction wrench often breaks because of the great force required for loosening the coupling.
The present invention overcomes the above undesirable features of removing a coupling from the rod by the provision of an apparatus that automatically engages the coupling member and rotates the rod to thereby break the threaded connection that joins the rod and coupling together, so that the coupling can subsequently be easily removed by hand.